混凝土断裂韧度K_(ⅡC)的试验研究

Experimental study on fracture toughness K_(Ⅱc) of concrete

采用国际上新近提出的两端切口Ⅱ型断裂试件,开展混凝土Ⅱ型断裂试验。试验观测到裂缝起裂角θ0约为0°,且沿韧带方向扩展;裂缝尖端韧带出现具有典型剪切特征的混凝土碎片,表明发生了剪切破坏模式。由试验测定的曲线上的特征点确定临界荷载Pc,进而由此试件几何相应的应力强度因子公式计算出混凝土Ⅱ型断裂韧度KⅡc约为KⅠc的2倍多。试验结果表明,两端切口Ⅱ型断裂试件是进行混凝土Ⅱ型断裂试验及测试混凝土KⅡc合适的试件形式。

Experimental study on concrete fracture of mode Ⅱ has been carried out by using the specimens of double-edge notched mode Ⅱ . Experimental results show that initial crack angle is approximately 0° and the crack extends along the direction of ligament. It is observed that the concrete fragments with typical shear fracture exist on the fracture surface in the front of the crack tip. It is shown that a shear crack develops at the notch tip and crack extension behaves a shear failure matter. The critical load is determined by the characteristic point of the measured curves. Then the fracture toughness KⅡc of concrete is calculated by the analytical formula. The results of experiments show that KⅡc values are about twice as large as KⅠc values obtained by other researchers. The experimental study has proven that this specimen is suitable for mode Ⅱ fracture testing to determine the fracture toughness KⅡc of concrete.